1. Field of the Invention
The present invention is concerned with an electrical switch which is located in line with a control cable, whereby application of tension to an inner core forming a part of the control cable brings electrical contacts into engagement for actuation of the switch. More particularly, it is concerned with an inline conduit switch which prevents overstressing of the contacts and isolates them from the surrounding environment.
2. Description of the Prior Art
Control cables are well known to those skilled in the art and as used herein, such control cables include a inner core typically of wire and a surrounding protective conduit or sheath. Their use is well known in a variety of applications such as fork lifts, utility vehicles, automobiles and light trucks, and lawn mowers and other powered equipment. The inner core of the control cable is able to shift within the conduit or sheath to actuate a controllable device. Such controllable devices may include, for example, a handbrake, a power takeoff mechanism, a drive engagement, or any other of a number of different devices which are intended to be manually actuated by a control cable. One end of the control cable is connected to a manually actuated control, for example a push-pull control, button, or lever, and the other to the device to be operated. Manually engaging the control exerts a tensioning force on the inner core, which in turn actuates the controllable device.
In many instances, it is desired to have an electrical function be carried out simultaneously with the manual actuation. For example, it may be useful for the operator to have a light, such as an indicator light, illuminate to show and confirm that the control has been actuated and that the controllable device is and remains engaged. Heretofore, this electrical operation has typically been carried out by an electrical microswitch operated by the control mechanism. Such microswitches, however, have a number of drawbacks. They are relatively expensive, must be separately installed on the control mechanism, are subject to fouling when used in muddy or other hostile environments, and may provide a false indication of operation. In regard to this latter condition, such microswitches mounted to control mechanisms may show that, for example, the handbrake has been applied and is operating, when in fact the control cable is broken and no tension is being applied to actuate the controllable mechanism.
Another switch has heretofore been developed which is positioned in line with the control cable, but this switch is not designed for rugged environments, and is designed as a low force momentary switch. While useful in such applications, it does not function as a conduit guide, is not sealed against the entry of external contaminants such as mud, and requires a biasing member be located between the contacts to maintain their separation until desired. Further, the aforementioned switch was developed for light duty applications with little conduit support, such that it is subject to damage in heavy duty environments where any significant transverse deflection of the conduit occurs.
Thus, there is a need for an improved inline conduit switch which overcomes these drawbacks with existing microswitches and the aforementioned inline switch, and also provides additional improvements.